Category Archives: Flavonoids

Abstract

The purpose of this study was to examine the effects of green tea extract (GTE) intake on bone structural and physiological properties, such as bone mass, trabecular bone microarchitecture, cortical bone geometry, and bone mechanical strength, in growing rats. Four-week-old male Wistar rats were divided into the following four eenoups: standard diet feeding for 85 days (S-CON) or 170 days (L-CON), and GTE diet feeding for 85 days (S-GTE) or 170 days (L-GTE). At the end of the experiment, in addition to measurement of circulating bone formation/resorption markers, bone mass, trabecular bone microarchitecture, and cortical bone geometry were analyzed in the left femur, and bone mechanical strength of the right femur was measured. There was no difference in all bone parameters between the S-CON and S-GTE groups. On the other hand, the L-GTE group showed the decrease in some trabecular bone mass/microarchitecture parameters and no change in cortical bone mass/geometry parameters compared with the L-CON group, and consequently the reduction in bone weight corrected by body weight. There was no difference in bone formation/resorption markers and bone mechanical strength between the S-CON and S-GTE groups and also between the L-CON and L-GTE groups. However, serum leptin levels were significantly lower in the L-GTE group than in the L-CON group. Thus, the long-term GTE intake had negative effects on bone, especially trabecular bone loss and microarchitecture mal-conformation, in growing rats.

Abstract

Effect of Hesperidin With and Without a Calcium (Calcilock) Supplement on Bone Health in Postmenopausal Women.

Citrus fruits contain unique flavanones. One of the most abundant of the flavanones, hesperidin, has been shown to prevent bone loss in ovariectomized rats.
The objective of the study was to measure the effect of hesperidin with or without calcium supplementation on bone calcium retention in postmenopausal women. The study was a double-blind, placebo-controlled, randomized-order crossover design of 500 g hesperidin with or without 500 mg calcium supplement in 12 healthy postmenopausal women. Bone calcium retention was determined from urinary excretion of the rare isotope, (41)Ca, from bone. Calcium plus hesperidin, but not hesperidin alone, improved bone calcium retention by 5.5% (P < .04). Calcium supplementation (Calcilock), in combination with hesperidin, is effective at preserving bone in postmenopausal women.

Abstract

The ability of hesperidin compared to that of insulin for preventing osteoporosis induced by type I diabetes in young male albino rats: A histological and biochemical study.

Patients with type I diabetes are at increased risk of osteoporosis even after insulin therapy in adult stage. This study was conducted to compare the efficacy of hesperidin (hesp) therapy versus that of insulin alone in the alleviation of osteoporosis arising from type I diabetes mellitus (T1DM) in young rats.
Hesperidin was administered orally to STZ-induced diabetes. The animals were evaluated morphologically and biochemically and compared with that received daily SC injections of long-acting insulin.
Histologically, we observed the degeneration of osteoblasts and osteocytes, decreased collagen fibers, and disturbed bone turn over markers in untreated DM rats. Hesperidin+ insulin supplementation to diabetic rats caused significant improvement of most of the bone histological and morphometric parameters compared with the insulin-treated group. Furthermore, hesp treatment significantly reduced pro-inflammatory mediators TNFα and NF-κB and increased serum biochemical markers of bone turnover, including osteopontin (OPN), osteocalcin (OC) and decreased serum alkaline phosphatase (ALP).
These data demonstrated that hesp could be considered to be a beneficial drug for preventing diabetic osteoporosis in growing age.

Abstract

Icariin is a prenylated flavonol glycoside contained in the herb Epimedium, which has long been used to improve bone fracture healing or prevent osteoporosis because of the belief that the herb has bone-strengthening action. We have previously demonstrated that icariin enhances the osteogenic differentiation of rat bone marrow stromal cells, and partially explained the bone-strengthening mechanism of the herb. In the present study, the effect of icariin on osteoclastogenesis and bone resorption activity was investigated in mouse bone marrow culture. It was found that icariin dose-dependently inhibited the growth and differentiation of hemopoietic cells from which osteoclasts were formed. Far less TRAP+ multinuclear cells appeared in the 10 microM icariin group than in the control. The bone resorption pits formed in the 10 microM icariin group was also significantly less than that of the control. RT-PCR analysis showed that the gene expression of TRAP, RANK and CTR was obviously lower than that of the control. It can be concluded that icariin has the ability to inhibit the formation and bone resorption activity of osteoclasts, which suggests that icariin should be the effective component for the bone-strengthening action of herb Epimedium.

Abstract

Icaritin and its glycosides enhance osteoblastic, but suppress osteoclastic, differentiation and activity in vitro.

Icariin, a principal flavonoid glycoside in Herba Epimedii, is hypothesized to possess beneficial effects on bone mass. Icariin is metabolized to icariside II and then to icaritin in vivo. In the present study, we investigated the in vitro effects of icariin, icariside II and icaritin on both osteoblasts and osteoclasts. After treatment with these compounds at concentrations 10(-5)-10(-8) mol/l, osteoblasts were examined for proliferation, alkaline phosphatase activity, osteocalcin secretion and matrix mineralization, as well as expression levels of bone-related proteins. The formation of osteoclasts was assessed by counting the number of multinucleated TRAP-positive cells. The activity of isolated rat osteoclasts was evaluated by measuring pit area, actin rings and superoxide generation. Icariside II and icaritin increased the mRNA expression of ALP, OC, COL-1 and OPG, but suppressed that of RANKL. In addition, these compounds reduced the number of multinucleated TRAP-positive cells and the osteoclastic resorption area. Also decreases were observed in superoxide generation and actin ring formation that are required for osteoclast survival and bone resorption activity. These findings suggest that icaritin, which was more potent than icariin and icariside II, enhanced the differentiation and proliferation of osteoblasts, and facilitated matrix calcification; meanwhile it inhibited osteoclastic differentiation in both osteoblast-preosteoclast coculture and osteoclast progenitor cell culture, and reduced the motility and bone resorption activity of isolated osteoclasts.

Abstract

Icariine stimulates proliferation and differentiation of human osteoblasts by increasing production of bone morphogenetic protein 2.

Icariine is a flavonoid isolated from a traditional Chinese medicine Epimedium pubescens and is the main active compound of it. Recently, Epimedium pubescens was found to have a therapeutic effect on osteoporosis. But the mechanism is unclear. The aim of the study was to research the effect of Icariine on the proliferation and differentiation of human osteoblasts.
Human osteoblasts were obtained by inducing human marrow mesenchymal stem cells (hMSCs) directionally and were cultured in the presence of various concentrations of Icariine. 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) test was used to observe the effect of Icariine on cell proliferation. The activity of alkaline phosphatase (ALP) and the amount of calcified nodules were assayed to observe the effect on cell differentiation. The expression of bone morphogenetic protein 2 (BMP-2) mRNA was detected by reverse transcriptase-polymerase chain reaction (RT-PCR).Icariine (20 microg/ml) increased significantly the proliferation of human osteoblasts. And, Icariine (10 microg/ml and 20 microg/ml) increased the activity of ALP and the amount of calcified nodules of human osteoblasts significantly (P < 0.05). BMP-2 mRNA synthesis was elevated significantly in response to Icariine (20 microg/ml).Icariine has a direct stimulatory effect on the proliferation and differentiation of cultured human osteoblast cells in vitro, which may be mediated by increasing production of BMP-2 in osteoblasts.

Abstract

Epimedium brevicornum maxim, a nonleguminous medicinal plant, has been found to be rich in phytoestrogen flavonoids. Results from a 24-month randomized double-blind placebo-controlled clinical trial showed that Epimedium-derived phytoestrogen flavonoids were able to exert beneficial effects on preventing bone loss in late postmenopausal women, without resulting in a detectable hyperplasia effect on the endometrium.
We performed a 24-mo randomized double-blind placebo-controlled clinical trial for evaluating the effect of the Epimedium-derived phytoestrogen flavonoids (EPFs) on BMD, bone turnover biochemical markers, serum estradiol, and endometrial thickness in postmenopausal women.
One hundred healthy late postmenopausal women, with a natural menopausal history within 10 approximately 18 yr and with a BMD T-score at the lumbar spine between -2 and -2.5 SD, were randomized into EPF treatment group (n = 50; a daily dose of 60 mg Icariin, 15 mg Daidzein, and 3 mg Genistein) or placebo control group (n = 50). All participants received 300 mg element calcium daily. BMD, bone turnover biochemical markers, serum estradiol, and endometrial thickness were measured at baseline and 12 and 24 mo after intervention.
Eighty-five participants completed the trial. The patterns of BMD changes were significantly different between the EPF treatment group and placebo control group by repeated-measures ANOVA (p = 0.045 for interaction between time and group at femoral neck; p = 0.006 for interaction between time and group at lumbar spine). BMD was found with a decreased tendency in the placebo control group at 12 (femoral neck: -1.4%, p = 0.104; lumbar spine: -1.7%, p = 0.019) and 24 mo (femoral neck: -1.8%, p = 0.048; lumbar spine: -2.4%, p = 0.002), whereas EPF treatment maintained BMD at 12 (femoral neck: 1.1%, p = 0.285; lumbar spine:1.0%, p = 0.158) and 24 mo (femoral neck: 1.6%, p = 0.148; lumbar spine: 1.3%, p = 0.091). The difference in lumbar spine between the two groups was significant at both 12 (p = 0.044) and 24 mo (p = 0.006), whereas the difference in the femoral neck was marginal at 12 mo (p = 0.061) and significant at 24 mo (p = 0.008). Levels of bone biochemical markers did not change in the placebo control group. In contrast, EPF intervention significantly decreased levels of deoxypyrdinoline at 12 (-43%, p = 0.000) and 24 mo (-39%, p = 0.000), except for osteocalcin at 12 (5.6%, p = 0.530) and 24 mo (10.7%, p = 0.267). A significant difference in deoxypyrdinoline between the two groups was found at both 12 (p = 0.000) and 24 mo (p = 0.001). Furthermore, neither serum estradiol nor endometrial thickness was found to be changed in either groups during the clinical trial.EPFs exert a beneficial effect on preventing bone loss in late postmenopausal women without resulting in a detectable hyperplasia effect on the endometrium.

Abstract

Effects of total flavonoids and flavonol glycosides from Epimedium koreanum Nakai on the proliferation and differentiation of primary osteoblasts.

In a bioassay-guided drug screening for anti-osteoporosis activity, eight flavonol glycosides were isolated from Epimedium koreanum Nakai, which is traditionally widely used in China for the treatment of impotence and osteoporosis. The effects of total flavonoids and flavonol glycosides on the proliferation and differentiation of rat calvarial osteoblast-like cells were evaluated by the MTT method and measuring the activity of alkaline phosphatase (ALP activity). Total flavonoids (1.2 x10(-2) to 6.0 x10(-7) mg/ml) and flavonol glycosides (2.0 x10(-5) to 1.0 x10(-9) mol/l) exhibited a strong inhibition on the proliferation of primary osteoblasts at most concentrations. However, the total flavonoids and icariin significantly promoted the differentiation of primary osteoblasts. The results suggested that flavonoids from E. koreanum Nakai may improve the development of osteoblasts by promoting the ALP activity; and icariin might be one of the active constituents facilitating the differentiation of osteoblasts.

Abstract

Involvement of aquaporin 9 in osteoclast differentiation.

Aquaporins (water channels) selectively enhance water permeability of membranes. Since osteoclast differentiation includes a dramatic increase in cell volume, we hypothesize that aquaporin(s) is/are critical for the formation of the multinucleated osteoclast from its mononuclear precursor. Our studies employ two cell models, bone marrow macrophages (BMMs) and the murine macrophage-like cell line, RAW264.7, as osteoclast precursors. Receptor activator of nuclear factor kappaB (NF-kappaB) ligand (RANKL) and macrophage-colony-stimulating factor or RANKL alone were used to induce osteoclast differentiation in BMMs or RAW264.7 cells, respectively. We first used qualitative reverse transcription (RT)-PCR to examine which of the aquaporins are expressed in osteoclasts and in their precursor cells. Out of the 10 aquaporins examined, only aquaporin 9 (AQP9) was expressed in osteoclast-lineage cells. AQP9 has unique aqueous pore properties mediating the passage of a wide variety of non-charged solutes in addition to water. Western analyses using specific antibodies revealed a higher AQP9 level in RANKL-treated than in untreated cells. Quantitative real-time RT-PCR analyses also demonstrated higher AQP9 mRNA levels in RANKL-treated cells. Finally, we examined the effect of phloretin, an AQP9 inhibitor, on RANKL-induced osteoclast differentiation. Cells were incubated with RANKL for 5 days, and phloretin was added for the last 2 days, when most fusion occurs. A dramatic reduction in osteoclast size and in the number of nuclei per osteoclast was observed in cultures containing phloretin. The inhibitor did not have a significant effect on the number and size of mononuclear phagocytes in cultures not treated with RANKL. Our results suggest a role for AQP9 in osteoclast differentiation, specifically in the fusion process.